The present invention relates to a lens advancing mechanism, and more particularly to a mechanism used to effect a telescoping operation of a zoom lens barrel.
Generally, in a zoom lens barrel, at least a pair of front and rear movable lens groups are moved along an optical axis on a predetermined locus in order to vary a focal length of the lens. The movable lens groups are normally guided along a linear path by using a guiding mechanism. Movement of the lens groups is accomplished by the action of a cam mechanism that is connected to an outside rotatable ring. Thus, by rotating the outside ring, the cam mechanism moves the lens groups along the linear path, as defined by the guiding mechanism, and thus a zooming operation is effected.
In the conventional lens, however, the guiding mechanism and the cam mechanism are provided separately, thus complicating the structure of the lens. This is illustrated in U.S. Pat. No. 4,993,815 and Japanese Patent Publication SHO 63-83712. This makes it difficult to manufacture the lens using resin material.